2002 Mercury Cougar • 160,000 miles

I have a 02 mercury cougar 2.5l it has been acting weird since my brothers changed the iac valve on it the idle will surge to 3 grand a really lound noise will come from under the hood and it will feel like some one is pressing on and off the throttle it has stalled once already. It had a pigeon cooing noise before so my brother did a intake gasket change once he did that I still had it then my brother changed the throttle body gasket egr gasket and put a new iac sensor on it and since then it has been a nightmare please help.
February 5, 2013.

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